1. What is Voltage? Remember, current is the flow (per second) of quantities of electrons past a point in a circuit. if 0.1 C of electrons pass this place in the circuit every second... then the current is 0.1 C per s, or 1 amp (1 A)

2. However, not all electrons are the same; some electrons have more potential energy than others. Since potential energy can be used to do work (loads do this work in circuits), if the electrons have a lot of potential energy, then they can do more work. The potential energy per quantity of electrons is called voltage, and is measured in volts.

3. Voltage is the Cause, Current is the Effect!

4. Voltage attempts to make a current flow, and current will flow if the circuit is complete. Voltage is sometimes described as the 'push' or 'force' of the electricity, it isn't really a force but this may help you to imagine what is happening. It is possible to have voltage without current, but current cannot flow without voltage.

5. Voltage and Current The switch is closed making a complete circuit so current can flow.

6. Voltage but No Current The switch is open so the circuit is broken and current cannot flow.

7. No Voltage and No Current Without the cell there is no source of voltage so current cannot flow.

8. Voltage Summary

9. Voltage is a measure of the energy carried by the charge. Strictly: voltage is the "energy per unit charge". Voltage is sometimes called potential difference, but this term is rarely used in electronics. Voltage is supplied by the cell or battery (or power supply). Voltage is used up in components/loads, but not in wires.

10. Voltage is measured in volts, V. Voltage is measured with a voltmeter, connected in parallel. We say voltage across a component. The symbol V is used for voltage in equations and is also the symbol for the units of voltage, the volt.